There are currently no effective treatments for cocaine addiction. The fact that hypothesis-driven research has not yet resulted in effective psychostimulant addition therapeutics highlights the need for novel approaches to this intractable problem. The current application will use a genome-wide, unbiased approach (RNA-seq) to identify novel transcripts altered by cocaine exposure. We will couple our RNA-seq analyses with an examination of chromatin accessibility in accumbens tissue derived from the same rats using the recently described assay for transposase-accessible chromatin using sequencing (ATAC-seq). These methodologies will be used in the context of the incubation of craving model in rats, in which the responding for cocaine- associated cues is progressively enhanced following periods of drug abstinence lasting weeks to months. Neither RNA-seq nor ATAC-seq analyses have been applied to the incubation of cocaine craving model to date. Very recent advances in ATAC-seq and RNA-seq methodologies succeeded in applying these powerful technologies to analyses of single nuclei. This is particularly relevant for the current proposal since it will allow us to differentiate in silico effects in the two major categories of accumbens neurons, those that express either D1-dopamine receptors (D1DRs) or D2DRs. Repeated cocaine produces opposing effects in these two classes of accumbens output neurons such that transmission through D1DR-expressing neurons is favored. Therefore, our over-arching hypothesis is that the incubation of cocaine craving at prolonged abstinence will be associated with more accessible chromatin and increased gene transcription in D1DR-containing neurons.
Specific Aim 1 will explore the nucleus accumbens epigenetic and transcriptional profiles associated with the incubation of cocaine craving.
Specific Aim 2 will confirm the functional relevance of the most prominent of the transcript changes by assessing the effect of viral-mediated manipulation of gene expression on the incubation of cocaine craving.
This project focuses on changes in gene expression and chromatin accessibility in the rat nucleus accumbens associated with the incubation of cocaine craving. Using state of the art RNA-seq and ATAC-seq technologies, we will identify transcript changes in the two major subtypes of nucleus accumbens neurons (i.e. D1DR- vs. D2DR-containing). The functional significance of observed changes will be achieved through over-expression or knockdown of chosen targets using a Cre-dependent AAV in recently-developed D1DR-Cre and D2DR-Cre transgenic rat lines.
